There are a couple ways of doing it. This is how I did it, but I wanted objects to be random areas on the landscape, so I used a collision trace for each random coordinate, to give me the exact world-space location. It looks a bit complex at first, but just continue to study it piece by piece and you will understand it to make your own variations in no time.You can also use a box collision and have your random coords be within that box.
Hopes this helps…
